Beware! This review will contain spoilers for Parasite, the first book in the Parasitology series! It’s kind of inevitable in a book 2 review, but unless you want to be spoiled, don’t read this review unless you’ve already read Parasite.
Symbiont is a good read. It has a lot of exciting moments and really great character building. The main issue I had with it is that it is very firmly a middle book; the plot doesn’t move forward all that much, and much of the book involves setting up what’s going to happen in the third novel in the series. Establishing power plays between the various players in the sleepwalker epidemic, in which people’s bioengineered tapeworms try to take over but end up just driving around zombie humans, is necessary, but at the same time, I feel like at the end of the book, Sal and her companions didn’t move that far forward from where they started, at least in terms of what’s actually happening.
In terms of who Sal is as a person? This book is basically dedicated to her coming to terms with who she actually is: a chimera. She’s not like the other sleepwalkers in that her implant integrated itself with Sally Mitchell’s brain so seamlessly that nearly no one realized who she really was. Sal also spends a lot of time surprising herself at what she’s capable of in terms of bravery and working through her fears and (mostly induced) neuroses.
As I mentioned, a lot of the plot in this book deals with establishing who the final players are as the United States is basically brought to its knees by the SymboGen implants trying to take over their human hosts. There are four corners: in one is SymboGen itself and the repulsively capitalistic Dr. Banks. In another is USAMRIID, the government agency run by Sally Mitchell’s father; they are ostensibly trying to save the remaining uninfected humans, but everything they do is sinister. Dr. Cale is in the third corner; one of the co-creators of the original implant, she is trying to study the sleepwalkers and the chimerae she helped create, but to what end? And in the last corner? The creepiest character to walk into a story full of creepy dudes: Sherman Lewis, one of Dr. Cale’s first chimerae, who is determined to make way for a new world order with tapeworms on top.
It’s difficult to talk about what actually happens without being intensely spoilery. In short, Sal bounces around between these four corners (often not of her own will), and she has to figure out both to whom she is loyal and to what she is loyal. She is a tapeworm that has merged with a human. How can she want to kill off the tapeworms to save the humans when she belongs to both?
I think my favorite thing in this book, though, is how it deals with the idea of personhood and self-determination. You wouldn’t normally think of a tapeworm or even a dog as a person, but Grant brings up the idea that if you are capable of making your own choices about your life, then you are a person. The tapeworms that have successfully integrated into chimera are people because they go beyond sentience and are capable of self-determination. The sleepwalkers, which run on pure instinct, are not. The best example of chimera-as-person isn’t Sal; it’s Ronnie, a chimera who has gone through several bodies. Ronnie is currently inhabiting a teenage girl’s body, but Ronnie knows he is male. His tapeworm is at its most basic genderless, but through his experiences in male human bodies, he has become male. It’s really fascinating.
If you’re already a fan of Grant’s work and enjoyed Parasite, then you’re going to enjoy Symbiont as the next step in Sal’s story. I would strongly recommend re-reading Parasite so it’s all fresh in your mind, as Symbiont starts up right where Parasite ends.